US11135068B2 - Interbody fusion implant - Google Patents

Abstract

An intervertebral implant can include a core and a flexible end plate. The core can have a core body that is elongate along a first direction and defines first and second outer surfaces. The flexible end plate can define an inner surface and an opposed bone facing surface that is configured to abut a vertebral body. The flexible end plate can be coupled to the core such that at least a portion of the inner surface faces the first outer surface and is spaced from the first outer surface. The flexible end plate is configured to resiliently flex toward a compressed configuration such that as the flexible end plate flexes toward the compressed configuration, a first end moves relative to the core along the first direction and the portion of the inner surface moves toward the first outer surface.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent application Ser. No. 13/653,715, filed on Oct. 17, 2012, which claims priority to U.S. Provisional Application No. 61/708,247, filed on Oct. 1, 2012, the contents of both of which are hereby incorporated by reference as if set forth in their entirety herein.

BACKGROUND

The placement of a fusion implant within an intervertebral space that is defined between adjacent vertebral bodies has typically resulted in the fusion of the adjacent vertebral bodies together. This “interbody fusion” procedure, which is in use today, is a widely accepted surgical treatment for symptomatic lumbar and cervical degenerative disc disease (DDD). The aim of a spinal fusion is to relieve pain caused by a degenerated disc, restore anatomy (disc height and/or lordotic curvature), and immobilize the affected level (fusion).

It has been found that the stiffness of the implants affects the rate of interbody fusion and that by reducing the stiffness of the implant the rate of interbody fusion can be increased.

SUMMARY

In an embodiment, an intervertebral implant can include a core and an end plate, the core can define a rear end and a front end that is spaced from the rear end along an insertion direction. The end plate can define a bone facing surface and an inner surface that is opposite the bone facing surface, the end plate further defining a first attachment member and a second attachment member that is spaced from the first attachment member, the first and second attachment members being movably coupled to the core such that at least a portion of the inner surface faces the core and is spaced from the core a first distance along a first direction that is substantially perpendicular to the insertion direction. The end plate is configured to resiliently move toward the core along the first direction such that 1) the portion of the inner surface is spaced from the core a second distance along the first direction that is less than the first distance, and 2) at least one of the first and second attachment members moves along the core.

In an embodiment, an intervertebral implant can include a core and a flexible end plate. The core can have a core body that is elongate along a first direction and defines first and second outer surfaces that are spaced from each other along a second direction that is perpendicular to the first direction. The flexible end plate can define an inner surface and an opposed bone facing surface that is configured to abut a vertebral body. The flexible end plate can be coupled to the core such that at least a portion of the inner surface faces the first outer surface and is spaced from the first outer surface by a distance. The flexible end plate can further define a first end and a second end that is spaced from the first end along the first direction. The flexible end plate is configured to resiliently flex toward a compressed configuration such that as the flexible end plate flexes toward the compressed configuration, the first end moves relative to the core along the first direction and the portion of the inner surface moves toward the first outer surface such that the distance is decreased.

In an another embodiment, an intervertebral implant can include a first end plate, a second end plate, and a biasing member coupled between the first and second endplates along a first direction. The first end plate can include a first body that defines a first bone facing surface and a first internal ceiling surface that is opposite the first bone facing surface along a first direction, the first end plate further including at least one wall that extends from the first body substantially along the direction, wherein the first end plate includes a cavity that is at least partially defined by the wall and the internal ceiling surface. The second end plate can include a second body that defines a second bone facing surface, the second body further defining a core having a second inner surface that is spaced from the second bone facing surface along the first direction, the core configured to be received in the cavity such that the second inner surface faces the internal ceiling surface. The first end plate is configured to move relative to the second end plate along the first direction between a first configuration and a second configuration whereby when in the first configuration the internal ceiling surface is spaced from the second inner surface along the first direction by a first distance, and when in the second configuration the internal ceiling surface is spaced from the second inner surface by a second distance that is less than the first distance, and movement of the first end plate from the first configuration to the second configuration causes the biasing member to compress so as to bias the first end plate along a direction from the second configuration toward the first configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of illustrative embodiments of the interbody fusion implant of the present application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the intervertebral implant of the present application, there is shown in the drawings illustrative embodiments. It should be understood, however, that the application is not limited to the precise arrangements and implants shown. In the drawings:

FIG. 1 is a perspective view of an intervertebral implant positioned in an intervertebral space that is defined between a superior vertebral body and an inferior vertebral body;

FIG. 2A is a perspective view of an intervertebral implant in accordance with an embodiment, the implant including a core, a first flexible end plate coupled to a first surface of the core, and a second flexible end plate coupled to a second surface of the core;

FIG. 2B is an exploded perspective view of the intervertebral implant shown inFIG. 2A;

FIG. 2C is a side elevation view of the intervertebral implant shown inFIG. 2A;

FIG. 2D is a top plan view of the intervertebral implant shown inFIG. 2A;

FIG. 2E is a front elevation view of the intervertebral implant shown inFIG. 2A;

FIG. 2F is a rear elevation view of the intervertebral implant shown inFIG. 2A;

FIG. 3A is a perspective view of an intervertebral implant in accordance with another embodiment, the intervertebral implant including a first end plate that defines a cavity, a second end plate that defines a core, and a biasing member positioned within the first and second end plates such that as the first end plate moves relative to the second end plate from an initial configuration toward a compressed configuration, the biasing member biases the first end plate toward the initial configuration;

FIG. 3B is an exploded perspective view of the intervertebral implant shown inFIG. 3A;

FIG. 3C is a side elevation view of the intervertebral implant shown inFIG. 3A;

FIG. 3D is a top plan view of the intervertebral implant shown inFIG. 3A;

FIG. 3E is a cross-sectional view of the intervertebral implant shown inFIG. 3A taken through theline3E-3E;

FIG. 3F is a front elevation view of the intervertebral implant shown inFIG. 3A; and

FIG. 3G is a rear elevation view of the intervertebral implant shown inFIG. 3A;

DETAILED DESCRIPTION

Referring toFIG. 1, a superiorvertebral body10adefines a first or superiorvertebral surface14aof anintervertebral space18, and an adjacent second or inferiorvertebral body10bdefines an inferiorvertebral surface14bof theintervertebral space18. Thus, theintervertebral space18 is disposed between or otherwise defined by thevertebral bodies10aand10b. Theintervertebral space18 can be disposed anywhere along the spine as desired, including at the lumbar, thoracic, and cervical regions of the spine. As illustrated, theintervertebral space18 is illustrated after a discectomy, whereby the disc material has been removed or at least partially removed to prepare theintervertebral space18 to receive an intervertebral implant, such asintervertebral implant22 that can achieve height restoration for example as shown inFIG. 1. The intervertebral implant can be configured as an interbody fusion implant and can be inserted into theintervertebral space18 along an insertion direction such as from a posterior approach. It should be appreciated, however, that theintervertebral implant22 can be inserted into theintervertebral space18 along any insertion direction such as from an anterior approach.

Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, “left”, “lower” and “upper” designate directions in the drawings to which reference is made. The words “inner” or “distal” and “outer” or “proximal” refer to directions toward and away from, respectively, the geometric center of the implant and related parts thereof. The words, “anterior”, “posterior”, “superior,” “inferior,” “medial,” “lateral,” and related words and/or phrases are used to designate various positions and orientations in the human body to which reference is made and are not meant to be limiting. The terminology includes the above-listed words, derivatives thereof and words of similar import.

In Reference toFIGS. 2A-2F, theintervertebral implant22 is described herein as extending horizontally along a longitudinal direction “L” and lateral direction “A”, and vertically along a transverse direction “T”. Unless otherwise specified herein, the terms “lateral,” “longitudinal,” and “transverse” are used to describe the orthogonal directional components of various components. It should be appreciated that while the longitudinal and lateral directions are illustrated as extending along a horizontal plane, and that the transverse direction is illustrated as extending along a vertical plane, the planes that encompass the various directions may differ during use. For instance, when theintervertebral implant22 is implanted into theintervertebral space18 along an insertion direction I, the transverse direction T extends vertically generally along the superior-inferior (or caudal-cranial) direction, while the horizontal plane defined by the longitudinal direction L and lateral direction A lies generally in the anatomical plane defined by the anterior-posterior direction, and the medial-lateral direction, respectively. Accordingly, the directional terms “vertical” and “horizontal” are used to describe theintervertebral implant22 and its components as illustrated merely for the purposes of clarity and illustration.

As shown inFIGS. 2A and 2B, theintervertebral implant22 can include a core26 that has acore body28 that is elongate along a first direction, such as along the longitudinal direction L or along the insertion direction, and defines a first or upperouter surface30 and a second or lowerouter surface34 that is spaced from the firstouter surface30 along a second direction that is perpendicular to the first direction, such as along the transverse direction T. The intervertebral implant can further include a firstflexible end plate36 coupled to the firstouter surface30 of thecore body28, and a secondflexible end plate38 coupled to the second outer surface of thecore body28. Both the firstflexible end plate36 and the secondflexible end plate38 are configured to resiliently flex toward the core when theintervertebral implant22 is inserted into theintervertebral space18.

As shown inFIGS. 2A-2C, thecore body28 can define a first or posterior orrear end40 and a second or anterior orfront end44 and can include a pair ofside walls48 that extend from theposterior end40 to theanterior end44. Theside walls48 can be spaced from each other along a third direction, such as along the lateral direction A, such that thecore26 defines a cage. As shown, theside walls48 extend toward each other as theside walls48 extend from theposterior end40 toward theanterior end44 so as to define anose52 at theanterior end44. The core26 can be rigid and can be made from any suitable bio-compatible material such as metal or plastic. For example the core26 can be made from PEEK or Titanium, as desired.

As shown inFIG. 2B, the core26 can further include at least onewindow56 that extends through thecore body28 along the third direction such as through theside walls48 along the third direction. In the illustrated embodiment, thecore26 includes twowindows56 that extend through thecore body28. It should be appreciated, however, that the core26 can include any number ofwindows56 and can alternatively be void ofwindows56 as desired. Thewindows56 are configured to promote boney in-growth. As shown inFIG. 2B, the core26 can also include at least onechannel60 that extends through thecore body28 along the second direction from the firstouter surface30 to the secondouter surface34. As with thewindows56, thechannel60 is configured to at least promote boney in-growth.

With continued reference toFIGS. 2A-2F, the firstflexible end plate36 defines aninner surface62 and an opposedbone facing surface64 that is configured to abut a vertebral body such as thevertebral body10awhen the intervertebral implant is disposed within theintervertebral space18. As shown inFIG. 2C, the firstflexible end plate36 can be coupled tocore26 such that at least a portion of theinner surface62 faces the firstouter surface30 and is spaced from the firstouter surface30 by a first distance D₁. The first distance D₁can be a maximum distance that theinner surface62 is spaced from the firstouter surface30 and can be taken at a longitudinal midline of the first flexible end plate36 (e.g. halfway between first and second ends of the first flexible endplate36). It should be appreciated, however, that the first distance D₁can be taken at any point along the firstflexible end plate36.

As shown inFIGS. 2B and 2C, the firstflexible end plate36 can define a first orposterior end70 and a second oranterior end74 that is spaced from thefirst end70 along the first direction. The first and second ends70 and74 can be coupled to thecore body28 such that the firstflexible end plate36 is bowed along the first direction. Theflexible end plate36 is flexible between a first or initial configuration and a second or compressed configuration such that as theend plate36 flexes toward the compressed configuration the distance D₁is decreased or the at least a portion of theinner surface62 is spaced from the firstouter surface30 by a second distance that is less than the first distance D₁. That is, the firstflexible end plate36 is configured to resiliently flex toward the compressed configuration such that as the flexible end plate flexes toward the compressed configuration, thefirst end70 moves along the core26 or at least relative to thecore26 along the first direction and the portion of theinner surface62 that faces the firstouter surface30 moves toward the firstouter surface30 such that the distance D₁is decreased. Similarly, thesecond end74 is configured to move along the core26 or at least relative to thecore26 along the first direction and away from thefirst end70 when the firstflexible end plate36 flexes toward the compressed configuration. When in the initial configuration the distance D₁can be between about 0.5 mm and about 10.0 mm and when in the compressed configuration the second distance can be about 0.0 mm. It should be appreciated, however, that the first and second distances can be any number as desired when the firstflexible end plate36 is in the initial configuration or in the compressed configuration. Moreover, it should be appreciated, that while in the illustrated embodiment both the first and second ends70 and74 are configured to move along the first direction, in certain embodiments one of the first and second ends70 and74 can be fixed.

As shown inFIG. 2D, the first and second ends70 and74 of the firstflexible end plate36 can include first andsecond attachment members79aand79bsuch that the attachment members can be movably coupled to thecore body28 proximate to the posterior and anterior ends40 and44 of thecore body28. As shown, the first andsecond attachment members79aand79bcan define first andsecond slots80aand80b, respectively, which are elongate along the first direction and are carried by the first and second ends70 and74, respectively. As shown inFIG. 2B,implant22, or at least thecore26 of the implant, can include first andsecond fixation members82aand82bthat extend through the first andsecond slots80aand80band into the firstouter surface30 of thecore body28 to thereby couple the firstflexible end plate36 to thecore body28. The firstflexible end plate36 can be coupled to thecore body28 such that the first andsecond fixation members82aand82blimit the movement of the first and second ends70 and74 of theend plate36 along the first direction when theflexible end plate36 flexes toward the compressed configuration.

As shown inFIG. 2B, the first andsecond fixation members82aand82bcan be pins that couple to thecore body28 through an interference fit. For example, thefixation members82aand82bcan include ashaft84 and ahead86 that extends out from an end of theshaft84. Thehead86 can be configured to have a dimension that is greater than that of a lateral dimension of theslots80aand80band theshaft84 can be configured to have a dimension that is less than the lateral dimension of theslots80aand80b. Therefore, the first and second ends70 and74 can be coupled to thecore body28 while at the same time be capable of translating along the first direction. It should be appreciated, however, that thefixation members82aand82bcan have any configuration as desired. For example, thefixation members82aand82bcan be threaded. Moreover, it should be appreciated that the first and second ends70 and74 can be coupled to thecore body28 with structure other than fixation members. For example, thecore body28 can define slots that are configured to translatably receive the first and second ends70 and74.

As shown inFIG. 2D, the firstflexible end plate36 can define a middle region89 that extends from thefirst attachment member79ato thesecond attachment member79b. The firstflexible end plate36 can include at least onechannel90 that extends through the middle region89 from theinner surface62 to thebone facing surface64 such that the at least onechannel60 of thecore26 and the at least onechannel90 of theflexible end plate36 are substantially aligned along the second direction. The alignedchannels60 and90 can help promote boney in-growth after theimplant22 has been inserted into theintervertebral space18. Furthermore, theflexible end plate36 can define a plurality ofteeth94 that extend out from thebone facing surface64. Theteeth94 can be configured to prevent migration of theintervertebral implant22 after theimplant22 has been inserted into theintervertebral space18.

As the first and second ends slide along thecore26, an entirety of the middle region89 can be spaced from thecore26 along the first direction. It should be appreciated, however, that in some embodiments, as the first and second ends slide along the core26 portions of the middle region89 can be in contact with thecore26. Moreover, it should be appreciated, that while the first andsecond attachment members79aand79bor at least the first and second ends70 and74 are illustrated as sliding along the firstouter surface30, the first andsecond attachment members79aand79bor at least the first and second ends70 and74 can slide along inner surfaces defined by thecore26.

With continued reference toFIGS. 2A-2F, the secondflexible end plate38 can be substantially identical to the firstflexible end plate36 and can include like structure unless otherwise described. It should be appreciated, however, that while in the illustrated embodiment the first and secondflexible end plates36 and38 are substantially identical, theend plates36 and38 can include different structure and have different shapes as desired.

As shown inFIG. 2B, the secondflexible end plate38 defines aninner surface162 and an opposedbone facing surface164 that is configured to abut a vertebral body such asvertebral body10b. As shown inFIG. 2C, the secondflexible end plate38 can be coupled tocore26 such that at least a portion of theinner surface162 faces the secondouter surface34 and is spaced from the secondouter surface34 by a third distance D₂. The third distance D₂can be a maximum distance that theinner surface162 is spaced from the secondouter surface34 and can be taken at a longitudinal midline of the second flexible end plate38 (e.g. halfway between first and second ends of the second flexible endplate38). It should be appreciated, however, that the second distance D₂can be taken at any point along the secondflexible end plate38, as desired.

As shown inFIG. 2C, the secondflexible end plate38 can define a first orposterior end170 and a second or anterior end174 that is spaced from thefirst end170 along the first direction. The first and second ends170 and174 can be coupled to thecore body28 such that the secondflexible end plate38 is bowed along the first direction. Theflexible end plate38 is flexible between a first or initial configuration and a second or compressed configuration whereby the distance D₂is decreased or the at least a portion of theinner surface162 is spaced from the secondouter surface34 by a fourth distance that is less than the third distance. That is, the secondflexible end plate38 is configured to resiliently flex toward the compressed configuration such that as the flexible end plate flexes toward the compressed configuration, thefirst end170 moves relative to thecore26 along the first direction and the portion of theinner surface162 moves toward the secondouter surface34 such that the distance D₂is decreased. Similarly, the second end174 is configured to move relative to thecore26 along the first direction and away from thefirst end170 when the secondflexible end plate38 flexes toward the compressed configuration. When in the initial configuration the third distance D₂can be between about 0.5 mm and about 10.0 mm and when in the compressed configuration the fourth distance can be about 0.0 mm. It should be appreciated, however, that the third and fourth distances can be any number as desired when the secondflexible end plate38 is in the initial configuration or in the compressed configuration. Moreover, it should be appreciated, that while in the illustrated embodiment both the first and second ends170 and174 are configured to move along the first direction, in certain embodiments one of the first and second ends170 and174 can be fixed.

As shown inFIG. 2B, the first and second ends170 and174 of the secondflexible end plate38 can be moveably coupled to thecore body28 proximate to the posterior and anterior ends40 and44 of thecore body28. As shown, the secondflexible end plate38 can include first andsecond attachment members179aand179bsuch that the attachment members can be movably coupled to thecore body28 proximate to the posterior and anterior ends40 and44 of thecore body28. As shown, the first andsecond attachment members179aand179bcan define first andsecond slots180aand180bthat are elongate along the first direction and located proximate to the first and second ends70 and74, respectively. As shown inFIG. 2B, the core26 can include third andfourth fixation members182aand182bthat extend through the first andsecond slots180aand180band into the secondouter surface34 of thecore body28 to thereby couple the secondflexible end plate38 to thecore body28 such that the third andfourth fixation members182aand182blimit the movement of the first and second ends170 and174 along the first direction when theflexible end plate38 flexes toward the compressed configuration.

It should be appreciated that while the firstflexible end plate36 is coupled to thecore body28 with first andsecond fixation members82aand82band thesecond end plate38 is coupled to thecore body28 with third andfourth fixation members182aand182b, the first and secondflexible end plates36 and38 can be coupled to thecore body28 using a first fixation member that extends through thecore body28 and through bothfirst slots80aand180a, and a second fixation member that extends through the core body and through bothsecond slots80band180b.

The first and secondflexible end plates36 and38 can be made from any bio-compatible material as desired. For example, the first and secondflexible end plates36 and38 can be made from a bio-compatible metal such as Titanium, Steel, or any material that can provide spring-action. The first andsecond end plates36 and38 can also have a stiffness that is configured to support or otherwise match the stiffness of thevertebral bodies10aand10b. For example, the modulus of elasticity of cortical bone is between 7 and 30 GPa and the first andsecond endplates36 and38 can have a stiffness that is configured to support this range of moduli. Therefore, the first andsecond endplates36 and38 can have a stiffness that is between about 7 GPa and about 30 GPA. It should be appreciated, however, that the first andsecond end plates36 and38 can have any stiffness as desired. For example, the modulus of elasticity of cancellous bone is 55.6 MPa and the first andsecond end plates36 and38 can have a stiffness that is about 55.6 MPa to thereby match the stiffness of the cancellous bone in the rare case that the cortical bone is lost and the cancellous bone is exposed. It should be appreciated, that the stiffness of theend plates36 and38 can be dependent on a variety of factors such as the material choice and the geometry of theend plates36 and38.

Theimplant22 can be sold individually or as a kit that includes the core26, a plurality offlexible end plates36 and38, and a plurality of fixation members. At least one of theend plates36 and38 can have a stiffness that is different than the stiffness of at least one of the other flexible end plates. It should be appreciated, however, that some of the end plates of the plurality of end plates can have the same stiffness. Moreover, it should be appreciated, that the end plates of the plurality of end plates can have different shapes, be made from different materials, and/or have different coupling features.

Now in reference toFIGS. 3A-3F, anintervertebral implant222 in accordance with another embodiment can include afirst end plate226, asecond end plate230 coupled to thefirst end plate226, and a biasingmember234 coupled between the first andsecond end plates226 and230 along a first direction. Thefirst end plate226 is configured to move relative to thesecond end plate230 along the first direction, such as along the transverse direction, between an initial or first configuration and a compressed or second configuration and movement of the first end plate from the first configuration to the second configuration causes the biasingmember234 to compress so as to bias the first end palate along the first direction from the second configuration toward the first configuration.

As shown inFIGS. 3A-3E, thefirst end plate226 includes afirst body240 that is elongate along a second direction, such as along the longitudinal direction or insertion direction. Thefirst body240 defines a firstbone facing surface244 and a first inner orinternal ceiling surface248 that is spaced from the firstbone facing surface244 along a first direction, such as along the transverse direction. Thefirst body240 can define a first orposterior end252 and a second oranterior end256. Thefirst end plate226 can further include at least one wall that extends from thefirst body240 substantially along the first direction. For example, thefirst end plate226 can include a pair ofside walls260 that extend from theposterior end252 to theanterior end256. Theside walls260 can extend toward each other as theside walls260 extend from theposterior end252 toward theanterior end256 so as to define anose258 at theanterior end256. Theside walls260 can be spaced from each other along a third direction, such as along the lateral direction A, such that theposterior end252, theanterior end256, and theside walls260 define acavity264 of the first body. Therefore, the at least one wall can be a single continuous wall that includes theposterior end252,anterior end256, andside walls260 such that thecavity264 is at least partially defined by the at least one wall and theinternal ceiling surface248.

In particular, thecavity264 can be defined by a first pair of internal side surfaces272 that are spaced along the second direction, and a second pair of internal side surfaces276 that are spaced along the third direction. As shown, the internal side surfaces272 of the first pair of side surfaces272 are spaced from each other along the second direction by a distance D₃. The distance D₃can be any dimension as desired so long as thecavity264 can receive a portion of thesecond end plate230.

As shown inFIG. 3E, thefirst end plate226 further includes arecess280 that extends into theinternal ceiling surface248 and toward the firstbone facing surface244. Therecess280 can be configured as a bore as illustrated and can be configured to receive a portion of the biasingmember234. It should be appreciated, however, that therecess280 can have any configuration as desired. For example, therecess280 can be substantially cubed shaped. Moreover, it should be appreciated, that theend plate226 can includemultiple recesses280 if desired.

With continued reference toFIGS. 3A-3E, thesecond end plate230 includes asecond body340 that is elongate along the second direction, such as along the longitudinal direction. As shown, thesecond body340 defines a secondbone facing surface344 and a secondinner surface348 that is spaced from the secondbone facing surface344 along the first direction, such as along the transverse direction. Thesecond body340 can define a first orposterior end352 and a second oranterior end356 that is spaced form theposterior end352 along the second direction. At least a portion of thesecond body340 defines a core364 that is configured to be received by thecavity264 of thefirst body240 such that theinternal ceiling surface248 faces the secondinner surface348. Therefore, thecore364 can be said to define the secondinner surface348.

Thecore364 can define a first pair of external side surfaces368 that are spaced along the second direction and a second pair of external side surfaces372 that are spaced along the third direction. The second pair of side surfaces372 extend toward each other as the side surfaces372 extend from theposterior end352 toward theanterior end356 such that thecore364 defines anose370 at theanterior end356. The external side surfaces368 of the first pair of external side surfaces368 are spaced from each other along the second direction by a distance D₄. The distance D₄can be substantially equal to the distance D₃such that thecore364 can be received within thecavity264. It should be appreciated, however, that the distance D₄can be any dimension as desired so long as thecavity264 can receive thecore364 of thesecond end plate230. Moreover, it should be appreciated that while in the illustrated embodiment thecore364 has shape that is substantially identical to that of thecavity264, in certain embodiments the shapes of the core and the cavity can be different so long as the cavity can receive the core.

The anterior and posterior ends252 and256 can trap thecore364 within thecavity264. Therefore, the anterior and posterior ends252 and256 can be said to be first and second attachment members. As thecore364 moves within thecavity264, the first and second attachment members move or otherwise will slide along the core along the first direction.

As shown inFIGS. 3B and 3E, thesecond end plate230 can further include ashoulder380 that extends out from thesecond body340 such that theshoulder380 defines anabutment surface384 that faces anend385 of the at least one wall. Theshoulder380 can be configured to limit movement of thefirst end plate226 relative to thesecond end plate230 along the first direction when theend385 abuts theabutment surface384. Theshoulder380 can extend completely around thesecond body340 and can be continuous as illustrated or theshoulder380 can be segmented as desired. It should be appreciated, however, that in certain embodiments, theinternal ceiling surface248 can abut the secondinner surface348 to thereby limit the movement of thefirst end plate226 relative to thesecond end plate230 along the first direction.

As shown inFIG. 3E, thesecond end plate230 further includes arecess392 that extends into the secondinner surface348 and toward the secondbone facing surface344. Therecess392 can be configured as a bore as illustrated and can be configured to receive a portion of the biasingmember234. It should be appreciated, however, that therecess392 can have any configuration as desired. For example, therecess392 can be substantially cubed shaped. Moreover, it should be appreciated, that the second end plate can include any number ofrecesses392 as desired.

The first andsecond end plates226 and230 can be made from any bio-compatible material such as PEEK and/or Titanium. Furthermore, at least one of thefirst end plate226 and thesecond end plate230 can include a radio-opaque marker398 that is configured to indicate the position of the implant during implantation. In the illustrated embodiment, thefirst end plate226 includes onemarker398 and thesecond end plate230 includes twomarkers398. It should be appreciated, however, that the first andsecond end plates226 and230 can include any number ofmarkers398 as desired, in any direction as desired, and of any shape (e.g. pin, ball, etc) as desired.

Furthermore, the first andsecond end plates226 and230 can define a plurality ofteeth400 that extend out from thebone facing surfaces244 and344. Theteeth400 can be configured to prevent migration of theintervertebral implant222 after theimplant222 has been inserted into theintervertebral space18. Moreover, it should be appreciated that the first andsecond endplates226 and230 can define channels and windows similar to those of theimplant22 to thereby further promote boney in-growth.

As shown inFIGS. 3B and 3E, the biasingmember234 can be positioned in therecesses280 and392 of the first andsecond end plates226 and230. Therefore, therecess280 of thefirst end plate226 can be coaxial with therecess392 of thesecond end plate230 when thecore364 is received by thecavity264 such that the biasingmember234 is trapped within therecesses280 and392. The biasingmember234 can be a spring such as a circular compression spring as illustrated. It should be appreciated, however, that the biasingmember234 can have any configuration as desired. For example, the biasingmember234 can be configured as a solid compression member.

The biasingmember234 can have a stiffness that is configured to support or otherwise match the stiffness of thevertebral bodies10aand10b. For example, the modulus of elasticity of cortical bone is between 7 GPa and 30 GPa and the biasingmember234 can have a stiffness that is configured to support this range of moduli. Therefore, the biasingmember234 can have a stiffness that is between about 7 GPa and about 30 GPA. It should be appreciated, however, that the biasingmember234 can have any stiffness as desired. For example, the modulus of elasticity of cancellous bone is 55.6 MPa and the biasingmember234 can have a stiffness of about 55.6 MPa.

As shown inFIG. 3E, when thefirst end plate226 is coupled to thesecond end plate230 at least one of thefirst end plate226 and thesecond end plate230 is configured to move relative to the other along the first or transverse direction between an initial or first configuration and a compressed or second configuration. When in the initial configuration, theinternal ceiling surface248 is spaced from the secondinner surface348 along the first direction by a first distance d₁. When in the compressed configuration, theinternal ceiling surface248 is spaced from the secondinner surface348 along the second direction by a second distance d₂that is less than the first distance d₁. Therefore, it can be said that when thefirst end plate226 moves toward the compressed configuration, the first distance d₁decreases. The first distance d₁can between about 0.5 mm and about 10.0 mm and the second distance d₂can be about 0 mm. It should be appreciated, however, that the first and second distances d₁and d₂can be any distances as desired.

When in the compressed configuration, the biasingmember234 is configured to bias thefirst end plate226 toward the initial configuration. It should be appreciated, however, that theimplant222 can include more than one biasingmember234 as desired. For example, theimplant222 can include two biasing members that bias thefirst end plate226 toward the initial configuration.

The first andsecond end plates226 and230 can be coupled together by the biasingmember234 or the at least one side wall can include fingers that engage the core so as to allow the core to move within the cavity along the first direction. It should be appreciated, however, that the first andsecond end plates226 and230 can be coupled together using any structure as desired so long as the core is capable of moving along the first direction within the cavity.

When theimplant22 or theimplant222 is inserted into theintervertebral space18 theimplants22 and222 can substantially match the stiffness of thevertebral bodies10aand10bto thereby promote fusion. Because of the construction of theimplants22 and222, theimplants22 and222 can be customized to match a variety of stiffnesses. Therefore, it can be said that in some embodiments theimplants22 and222 are customizable or have adjustable stiffnesses. It should be appreciated, however, that theimplants22 and222 can be constructed to have a specified stiffness.

While the foregoing description and drawings represent the preferred embodiments of the present invention, it will be understood that various additions, modifications, combinations and/or substitutions may be made therein without departing from the spirit and scope of the invention as defined in the accompanying claims. In particular, it will be clear to those skilled in the art that the invention may be embodied in other specific forms, structures, arrangements, proportions, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. One skilled in the art will appreciate that the invention may be used with many modifications of structure, arrangement, proportions, materials, and components, which are particularly adapted to specific environments and operative requirements without departing from the principles of the invention. In addition, features described herein may be used singularly or in combination with other features. For example, features described in connection with one embodiment may be used and/or interchanged with features described in another embodiment. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and not limited to the foregoing description.

It will be appreciated by those skilled in the art that various modifications and alterations of the invention can be made without departing from the broad scope of the appended claims. Some of these have been discussed above and others will be apparent to those skilled in the art.

Claims (18)

What is claimed:

1. An intervertebral implant comprising:

a leading end, and a trailing end that is spaced from the leading end along an insertion direction;

a core defining a rear end, a front end that is spaced from the rear end along the insertion direction, and first and second side surfaces that extend between the front end and the rear end along at least a middle of the core that is midway between the leading end and the trailing end of the implant; and

an end plate that defines:

a bone facing surface and an inner surface that is opposite the bone facing surface along a first direction, perpendicular to the insertion direction, such that the inner surface faces away from the bone facing surface and is positionally fixed relative to the first bone facing surface;

a recess that extends into the inner surface towards the bone facing surface and that is configured to receive a spring; and

a first attachment member, a second attachment member that is spaced from the first attachment member, and a cavity that extends from the inner surface along the first direction away from the bone facing surface and between the first and second attachment members such that the cavity receives at least a portion of the rear end, the front end, and the first and second side surfaces of the core, the first and second attachment members being movably coupled to the core such that at least a portion of the inner surface faces the core and is spaced from the core a first distance along a first direction,

wherein the end plate is configured to resiliently move toward the core along the first direction such that 1) the portion of the inner surface is spaced from the core a second distance along the first direction that is less than the first distance, and 2) at least one of the first and second attachment members has a terminal end that slides along the core such that the terminal end and core are movable relative to one another.

2. The intervertebral implant ofclaim 1, wherein the at least one of the first and second attachment members moves along the core along the first direction.

3. The intervertebral implant ofclaim 1, further comprising a spring between the core and the end plate.

4. The intervertebral implant ofclaim 3, wherein the spring is one of a coil spring, a circular compression spring, and a solid compression member.

5. The intervertebral implant ofclaim 1, wherein the core defines a rear surface at the rear end, and a front surface at the front end, and the pair of sides surfaces extend from the rear surface to the front surface.

6. The intervertebral implant ofclaim 1, wherein the core defines an inner surface that is configured to face the inner surface of the end plate, and the inner surface of the core extends from the front end to the rear end, and from the first side surface to the second side surface.

7. The intervertebral implant ofclaim 1, wherein the first and second attachment members are formed from a rigid material.

8. An intervertebral implant comprising:

a first end plate including a first body, the first body defining a first bone facing surface, and an internal ceiling surface that is opposite the first bone facing surface along a first direction such that the internal ceiling surface faces away from the first bone facing surface and is positionally fixed relative to the first bone facing surface, the first end plate further including at least one wall that is formed from a rigid material and that extends from the internal ceiling surface substantially along the first direction such that a cavity is at least partially defined by the at least one wall and extends from the internal ceiling surface away from the first bone facing surface, wherein the first end plate defines a recess that extends into the internal ceiling surface towards the first bone facing surface;

a second end plate including a second body that defines a second bone facing surface, the second body further defining a core having a second inner surface that is spaced from the second bone facing surface along the first direction, the core configured to be received in the cavity such that the second inner surface faces the internal ceiling surface; and

a spring coupled between the first and second endplates along the first direction and received in the recess;

wherein the first end plate is configured to move relative to the second end plate along the first direction between a first configuration and a second configuration whereby when in the first configuration the internal ceiling surface is spaced from the second inner surface along the first direction by a first distance, and when in the second configuration the internal ceiling surface is spaced from the second inner surface by a second distance that is less than the first distance, and movement of the first end plate from the first configuration to the second configuration causes the spring to compress so as to bias the first end plate along a direction from the second configuration toward the first configuration, and

wherein the at least one wall has a terminal end that slides along the core such that the terminal end and core are movable relative to one another.

9. The intervertebral implant ofclaim 8, wherein the second end plate defines a second recess that extends into the second inner surface and toward the second bone facing surface, and the spring is at least partially disposed in the second recess.

10. The intervertebral implant ofclaim 9, wherein the second end plate includes a shoulder that extends out from the second body, the shoulder defining an abutment surface that faces an end of the at least one wall such that the shoulder limits movement of the first end plate relative to the second end plate along the first direction when the end of the at least one wall abuts the abutment surface.

11. The intervertebral implant ofclaim 9, wherein the recess of the first end plate is coaxial with the second recess of the second end plate.

12. The intervertebral implant ofclaim 8, wherein the cavity is at least partially defined by opposed first side surfaces that are spaced from each other along a second direction that is perpendicular to the first direction by a third distance, and the core defines opposed second side surfaces that are spaced from each other along the second direction by a fourth distance that is substantially equal to the second distance.

13. The intervertebral implant ofclaim 8, wherein the spring is one of a coil spring, a circular compression spring, and a solid compression member.

14. The intervertebral implant ofclaim 8, wherein the spring has a stiffness that is between about 7 GPa and about 30 GPa.

15. The intervertebral implant ofclaim 8, wherein at least one of the first end plate and the second end plate includes a radiopaque marker.

16. The intervertebral implant ofclaim 8, wherein the first distance is between about 0.5 mm and about 10.0 mm.

17. The intervertebral implant ofclaim 8, wherein the first end plate and the second end plate are made from PEEK.

18. The intervertebral implant ofclaim 8, wherein the core defines a rear end, a front end that is spaced from the rear end along an insertion direction, and first and second side surfaces that extend between the front end and the rear end along at least a middle of the core that is midway between the front end and the rear end.

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